1. Field of the Invention
The present invention relates generally to cable adapters, and more particularly it relates to modular adapters.
2. Description of the Prior Art
In order that terminals or computer systems could have the capability of communicating with each other and other computer equipment, local area networks (LANs) were introduced so that terminals, computer systems, and other computer equipment could communicate within the same building. The type of local area network (LAN) used differed depending upon the speed, costs and the capability of wiring the terminals, computer systems, and equipment together.
One type of LAN was a token ring that utilized a continuous coaxial transmission cable that was configured as a ring. Male and female BNC connectors were used to couple the ring together. A T-connector or tap was inserted within the ring so that the various computer equipment could communicate with signals on the token ring. While a token ring provided fast communication, it was difficult to expand and any break in the ring caused the entire LAN to be inoperable.
Another type of LAN, referred to as ethernet, was introduced. An ethernet LAN provided for flexibility such that additional computers, other computer equipment, or other network equipment such as bridges, routers, or repeaters could be easily added. Failures in a portion of an ethernet LAN were more tolerated such that the entire network would not be disrupted. Initially, an ethernet LAN required routing expensive cabling throughout a building. To lower the costs of installing an ethernet, a 10BASE-T ethernet LAN was introduced which utilized modular connectors and cabling similar to modular telephone cables. A 10BASE-T ethernet simply required the use of eight twisted wire conductors or the equivalent of two four conductor telephone cables. A 10BASE-T ethernet was inexpensive and allowed a company to pre-wire an entire building for a LAN.
In order to connect the terminals, computer systems, and other computer equipment to the ethernet, connectors were necessary. The male connector used at an end of 10BASE-T cable was a modular plug referred to as an RJ-45 plug. A female connector used to receive the male RJ-45 plug was a modular jack referred to as an RJ-45 jack. The RJ-45 jack was not initially built into most terminals or computer systems because it was unknown what type of LAN connection would be used and it was prohibitively expensive to provide a connector for every type of LAN connection. Thus computer equipment manufacturers typically utilized a female D-type connector to provide a connection to the LAN interface electronics of the computer system. In order to couple the female D-type connector to a LAN connector, an adapter was required. In the case of 10BASE-T ethernet LAN, a modular adapter was introduced that converted an RJ-45 plug to a male D-type connector which could be plugged into a female D-type connector. The modular adapter also became useful in connecting modems, printers, and other peripheral components to the computer itself via the serial ports such as an RS-232 port or parallel ports.
With the increase in the number of computer systems, other computer equipment, and network equipment that was attached to the ethernet LAN, the communication over the ethernet became slower. In order to increase the speed of communication over the ethernet LAN, new communication standards are being introduced such that the speed and frequency of communication over an ethernet LAN will increase. The increase in speed and frequency will cause an increase in the frequency of signal transitions on the ethernet LAN.
Signal transitions in a typical wire cause a current to flow which generates an electromagnetic field about the wire. As the frequency in the signal transitions increase the strength of the electromagnetic field increases. An electromagnetic field around a wire can cause interference to radio-wave signals and even interfere with the signals on adjacent wires thereby causing faulty signals. Thus, increasing the frequency of communication over a LAN brings about an increase in signal transitions and a stronger electromagnetic field around the wires. In the case of 10BASE-T ethernet LAN, the increased signal transitions are introduced into the modular adapter possibly interfering with radio-wave signals external to the modular adapter and the signals propagating on adjacent conductors within the modular adapter. The cable connected to the modular adapter can amplify the electromagnetic radiation like an antenna if the electromagnetic radiation is allowed to propagate down the conductors of the cable and proper shielding is not present.
A modular adapter with the appropriate male or female connectors may be used to adapt from one connector to another other than RJ-45 and D-type connectors. In any case, it is desirable to reduce the electromagnetic interference that may interfere with radio-wave signals and adjacent conductors within a modular adapter.